Manufacture of fluorine



june 21, W32. H. KREKELER I MANUFACTURE OF FLUORINE Filed Dec. 4, 1930Patented June 21, 1932 HEINZ KBEKELEB, OI BERLIN, GERMANY,

PATENT OFFICE ASSIGNOR TO I. G. FARBENINDUSTRIE AKTIENGESELLSCHAFT, OFFRANKIORT-ON-THE-MAIN, GERMANY MANUFACTURE OF FLUORINE Application filedDecember 4, 1930, Serial No. 500,035, and in Germany December 5, 1929. i

The present invention relates to improvements in apparatus for themanufacture of fluorine by electrolysis of alkali metal fluorides and toimprovements in the process.

Various publications are avallable relating to the production offluorine. Fluorine has hitherto been manufactured principally inaccordance with the processes of Moissan and Argo, Mathers, Huniistonand Anderson. In all these processes the electrodes were inserted fromabove into the electrolyzing vessel and fluorspar was employed asjointing material for the fixation of the electrodes.

According to the present invention alkali metal fluorides, especiallydiand polyfluorides are subjected to electrolysis in appropriateapparatus which are manufactured from materials resisting the attack ofhydrofluoric acid and fluorine as, for instance, copper or magnesium.The electrolyzer is divided into two partitions, an anode and a cathodechamber in such a manner that the electrolyte and the current is allowedto pass 2 from one chamber to the other, but the gases evolved, fluorideand hydrogen, are prevented from passing from one chamber to the other.This is accomplished by the employment of diaphragms or U-shapedelectrolyzing vessels or by any other means. Each chamber is providedwith a gas outlet and at least one chamber is also provided with anaperture allowing the introduction of anhydrous hydrofluoric acid. Oneelectrode consists of carbon, graphite or coke at which electrodefluorine is evolved and the other of carbon, graphite, coke or of silveror another metal which is not attackedby hydrofluoric acid, at whichelectrode hydrogen is evolved.

The current supply line for the electrodes passes through the walls ofthe electrolyzing vessel, but must be insulated therefrom and must befastened in the walls.

In accordance with the present invention the electrolyte itself in thesolid form is employed as the jointing and insulating material for thefixation of the electrodes. The advantages resulting incontradistinetion to the hitherto known processes signify an importanttechnical advance. The electrodes are introduced from below upwardlyinto the electrolyte or from above or from the sides by means of cups orsimilar acting devices.

The reaction is performed with the liquid electrolyte. It is necessarytherefor to heat the solid electrolyte to the melting point. Accordingto the kind of electrolyte used the heat required varies within widelimits in accordance with the melting points of the fluorides employed.The meltin point is the lower the more mols of hydroduoric acid areloosely bound to the monofluoride. The termpolyfluorides used in theclaims is intended to include alkali-metal-difiuorides as well as alkalimetal polyfluorides containing more than two mols of hydrofluoric acidbound to one mol of alkali metal fluoride.

The invention is illustrated by the following examples, without beinglimited thereto:

Ewample: (compare Fig. I

The limbs of a U-shaped electrolyzing vessel (1) have two attachmenttubes underneath. Through these are inserted electrodes (3) of knownmaterial and design. For the purpose of jointing a plate or disc (6') ofa metal, such as copper or magnesium may be employed, through which theelectrodes penetrate. Instead of metal plates, plates of an insulatingmaterial such asasbestos slate can likewise be used. After theelectrodes have been placed into the desired position both limbs (5) ofthe electrolyzing vessel are filled with thoroughly dried alkali metaldifluoride and freed from the last remaining 85 traces of moisture bypassing through a thoroughly dried current of hot air. When this isaccomplished the alkali metal difluoride is melted by an appropriateheating appliance and after all the alkali metal difluoride present inthe attachment tubes above the metal or insulating material plates ordiscs has become liquid it is caused to solidify and the metal plates ordiscs are removed in an appropriate manner while the plates or discsmade from insulating materials need not be removed. In order to preventmoisture penetrating through the attachment tubes these are now dippedinto a bath of liquid parafiin mo wax or similar material.

The electrolysis can now proceed. During the electrolysis hydrofluoricacid freed from water is added through the tube 4 in.

the same measure as fluorine and hydrogen are evolved from theelectrolyte. In this way the composition of the electrolyte ismainprevented by attaching a cooler (2) to the i any stoppage by themelt separate tubes through which the evolved hydrogen and fluorineescapes. The hydrogen fluoride can only evaporate through these tubes.At this point the tubes are advantageously expanded like a steamdome inorder to revent there. Here also a sort of reflux condenser is attachedwhich prevents any evaporation of hydrogen fluoride. At the same tlme agreater partial pressure of hydrogen fluoride above the melt is obtainedso that by this means also the evaporation of hydrogen fluoride isrestrained. Instead of alkali metal difiuoride alkali metalpolyfluoride, produced by the subsequent passing in of hydrogen fluorideinto the alkali metal difluoride, can likewise be used for electrolysis.

It may likewise be of advantage in the case of complicated apparatus: tointroduce the electrodes from above or from the sides (see Fig. II). Inthis arrangement also solidified electrolyte (5) that is to say solidalkali metal dior polyfluoride, is employed as the jointing material.Instead of a U-shaped electrolyzing vessel as described above an otherappropriate electrolyzing vessel (13 may be employed as, for example, anelectrolyzlng vessel of cylindrical or angular shape, containingdiaphragms (9) which allow the passage of the electrolyte from thecathode to theanode chamber, but prevents the passage of ases from onechamber to the other.

11 this drawin cups (7 attached to the tubes by which t e current supplfor the electrodes penetrate the walls are lled with the solidelectrolyte (5). Into the solid electrolyte dip caps (8) which arefastened to the current supply for the electrodes, whereby a closeinsulation is attained.

I claim:

1. Anelectrolyzin ap aratus for the N- duction of fluorine y eectrolysis of a ali metal polyfluorides comprising a vessel beingdivided in an anode and a cathode chamber, said chambers being connectedby means allowing the passage of the electrolyte and the current fromone chamber to the other, but not allowing the gases evolved to passfrom one chamber to the other, an electrode in each of the chambers,each electrode being provided with a current supply said current supplypassing through the walls of the apparatus but being insulated fromdirect contact with the walls by a layer of solid electrolyte and beinfastened by the solid electrolyte in the wa of the apparatus, eachchamber being provided with a gas outlet and at least one chamber beingprovided with an aperture allowing the introduction of hydrofluoric acidand a heating appliance allowing each chamber, current supplying meansconnected with said electrodes, the current supplyin means and theelectrodes being insulated mm the vessel by means of a solid layer ofelectrolyte interposed between said vessel and said electrodes andcurrent supply means, means for removing evolved as from the chambersand means for intro ucing parent materialto the vessel.

3. An apparatus for the production of fluorine by electrolysiscomprising a vessel divided into an anode and a cathode chamber by meanspermitting the passage of the electrolyte from one chamber to anotherbut not permitting the evolved gases to pass from one chamber toanother, an electrode within each chamber, current supplying meansconnected with said electrodes, the current supmeans and the electrodesbein insulated roin the vessel by means of a solld layer of electrolyteinterposed between said vessel and said electrodes and current supplymeans, each chamber being provided with a gas outlet and at least onechamber being provided with an aperture allowing the introduction of liuid parent material.

11 testimony whereof, I afiix my signature.

. HEINZ KREKELER.

